Interference-type optical magnetic field sensor device

Abstract

To provide an interference type optical magnetic sensor device with which it is possible to remove the effects of polarized wave crosstalk.SOLUTION: An interference type optical magnetic sensor device comprises: a first light emission part for emitting first linearly polarized wave light; a second light emission part for emitting non-polarized light; a magnetic sensor for emitting return light of incident light and disposed inside of a magnetic field; an optical unit having a first port on which the first linearly polarized wave light and the non-polarized light are incident, a second port on which the return light of incident light after having been emitted to a magnetic sensor element is incident, third and fourth ports for emitting first and second rays of linearly polarized light derived by splitting the return light of the first linearly polarized wave light among the rays of return light, and fifth and sixth ports for emitting a P-polarization component and a S-polarization component derived by splitting the return light of the non-polarized light; a detection signal generation part for receiving the first and second rays of linearly polarized light and outputting a detection signal that corresponds to the magnetic field; a crosstalk compensation circuit for receiving the return light of the non-polarized light and outputting a disturbance signal that corresponds to polarized wave crosstalk; and a signal processing circuit for receiving the detection signal and the disturbance signal and outputting a difference signal between the two.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an interference-type optical magnetic field sensor device. [Background technology]

[0002] An interferometric optical magnetic field sensor device is known that photoelectrically converts light transmitted through a Faraday rotator placed at the tip of an optical fiber to generate a detection signal corresponding to the magnetic field applied to the Faraday rotator (for example, Patent Document 1). The interferometric optical magnetic field sensor device disclosed in Patent Document 1 inverts and amplifies the differential signal of an electrical signal proportional to the respective intensities of the S-polarized component and the P-polarized component to generate a detection signal from which the DC component has been removed, thereby making it possible to increase the S / N ratio of the detection signal corresponding to the magnetic field to be detected.

[0003] Furthermore, a ring interferometer has been reported that has significantly improved resistance to polarization crosstalk caused by temperature changes and bending of the optical fiber (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-126007 [Patent Document 2] Patent application No. 2021-045982 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional ring interferometers are not completely resistant to polarization crosstalk. The magnetic field sensor element, adhesive, wave plate, and optical fiber used in the sensor head are temperature-dependent, resulting in polarization crosstalk. This polarization crosstalk is the same as Faraday rotation. In other words, it is superimposed on the modulation generated in the sensor head, and problems such as reduced magnetic field detection accuracy or difficulty in detecting the magnetic field may arise if, for example, a temperature change occurs in the sensor head or bending stress occurs in the optical fiber.

[0006] The present invention is intended to solve such problems, and has an object to provide an interference-type optical magnetic field sensor device that can eliminate the influence of polarization crosstalk. [Means for solving the problem]

[0007] An interference-type optical magnetic field sensor device according to an embodiment of the present disclosure includes a first light-emitting unit that emits first linearly polarized light, a second light-emitting unit that emits unpolarized light, a magnetic field sensor element at least a portion of which can be arranged in a predetermined magnetic field and which emits returned light in response to incident light, a first port into which the first linearly polarized light and unpolarized light are incident, a second port from which the incident light is emitted to the magnetic field sensor element and into which the returned light is incident, a third port and a fourth port from which a first linearly polarized light and a second linearly polarized light orthogonal to the first linearly polarized light are respectively output, and a return port from which the returned light is split. the magnetic field sensor element includes an optical unit having a fifth port and a sixth port that respectively emit P-polarized and S-polarized components obtained by splitting non-polarized returning light from the reflected light; a detection signal generating unit that receives the first linearly polarized light and the second linearly polarized light and converts them into electrical signals to output a detection signal corresponding to the magnetic field applied to the magnetic field sensor element; a crosstalk compensation circuit that receives the P-polarized and S-polarized components and converts them into electrical signals to output a disturbance signal corresponding to polarization crosstalk; and a signal processing circuit that receives the detection signal and the disturbance signal and outputs a differential signal between the detection signal and the disturbance signal.

[0008] In an interferometric optical magnetic field sensor device according to an embodiment of the present disclosure, it is preferable that the wavelength of the first linearly polarized light is light in a first wavelength band, and the wavelength of the unpolarized light is light in a second wavelength band different from the first wavelength band.

[0009] In the interferometric optical magnetic field sensor device according to an embodiment of the present disclosure, the first wavelength band is preferably included in the C-band wavelength band, and the second wavelength band is preferably included in the O-band wavelength band.

[0010] In an interferometric optical magnetic field sensor device according to an embodiment of the present disclosure, the optical unit includes a first polarization element that, in response to incidence of first linearly polarized light, emits third linearly polarized light and fourth linearly polarized light orthogonal to the third linearly polarized light, and emits second linearly polarized light in response to incidence of fifth linearly polarized light and sixth linearly polarized light orthogonal to the fifth linearly polarized light; an optical path unit that is optically connected to the first polarization element and has a first optical path that propagates the third linearly polarized light and the sixth linearly polarized light, and a second optical path that propagates the fourth linearly polarized light and the fifth linearly polarized light; and an optical path unit that, in response to incidence of the second linearly polarized light from the first polarization element, converts the second linearly polarized light into the first linearly polarized light and and a third birefringent element that separates the first linearly polarized light and the fourth linearly polarized light incident from the first polarizing element into the first optical path and the second optical path, respectively, and combines the fifth linearly polarized light that has propagated through the second optical path and the sixth linearly polarized light that has propagated through the first optical path and output the combined light to the first polarizing element; and a second birefringent element that combines the third linearly polarized light that has propagated through the first optical path and the fourth linearly polarized light that has propagated through the second optical path and output the combined light to the second port, and separates the fifth linearly polarized light and the sixth linearly polarized light incident from the second port into the first optical path and the second optical path, respectively.

[0011] In an interference type optical magnetic field sensor device according to an embodiment of the present disclosure, it is preferable that the optical path section further includes a second optical element arranged in the first optical path and adjusting the phases of the third linearly polarized light and the sixth linearly polarized light so that the phase difference between the fifth linearly polarized light and the sixth linearly polarized light is 90 degrees.

[0012] In an interference type optical magnetic field sensor device according to an embodiment of the present disclosure, it is preferable to further include a third birefringence element that, in response to the second linearly polarized light being incident from the first polarizing element, splits the second linearly polarized light into the first linearly polarized light and a second linearly polarized light orthogonal to the first linearly polarized light.

[0013] In an interference type optical magnetic field sensor device according to an embodiment of the present disclosure, it is preferable that the device further includes a fourth birefringent element into which the first linearly polarized light and the second linearly polarized light are incident from the third birefringent element, and the first linearly polarized light is incident from the fourth birefringent element into the third port, and the second linearly polarized light is incident from the fourth birefringent element into the fourth port.

[0014] In the interferometric optical magnetic field sensor device according to an embodiment of the present disclosure, the first birefringent element, the second birefringent element, the third birefringent element, and the fourth birefringent element are preferably made of calcite.

[0015] In the interferometric optical magnetic field sensor device according to an embodiment of the present disclosure, the first birefringent element and the second birefringent element are preferably spatially coupled. [Effects of the Invention]

[0016] According to an embodiment of the present disclosure, an interferometric optical magnetic field sensor device capable of eliminating the influence of polarization crosstalk can be provided. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram of an interferometric optical magnetic field sensor device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a circuit block diagram of a first signal processing circuit of an interferometric optical magnetic field sensor device according to an embodiment of the present disclosure. [Figure 3] FIG. 4 is a circuit block diagram of a second signal processing circuit of the interferometric optical magnetic field sensor device according to the embodiment of the present disclosure. [Figure 4] FIG. 2 is a plan view of the optical unit shown in FIG. [Figure 5]FIG. 5 is a diagram showing the optical characteristics of the first birefringent element shown in FIG. [Figure 6] 5A is a diagram showing the optical path of the first linearly polarized light in the optical unit shown in FIG. 4, and FIG. 5B is a diagram showing the transition of the polarization plane of the first linearly polarized light shown in FIG. [Figure 7] 5A is a diagram showing the optical path of the second linearly polarized light in the optical unit shown in FIG. 4, and FIG. 5B is a diagram showing the transition of the polarization plane of the second linearly polarized light shown in FIG. [Figure 8] FIG. 10 is a plan view of an optical unit according to a modified example. [Figure 9] 9 is a diagram showing the optical path of a first linearly polarized light in the optical unit shown in FIG. 8. [Figure 10] 9 is a diagram showing the optical path of a second linearly polarized light in the optical unit shown in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an interference-type optical magnetic field sensor device according to the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present disclosure is not limited to the embodiments, but extends to the inventions set forth in the claims and their equivalents.

[0019] (Configuration and Function of Interferometric Optical Magnetic Field Sensor Device) FIG. 1 is a block diagram of an interferometric optical magnetic field sensor device according to an embodiment of the present disclosure.

[0020] The interference type optical magnetic field sensor device 100 has an optical unit 1, a first light emitting section 110, a second light emitting section 110a, a quarter wavelength plate 120, a plano-convex lens 130, a magnetic field sensor element 140, a detection signal generating section 150, a crosstalk compensation circuit 160, and a signal processing circuit 170, and outputs a detection signal according to the magnetic field applied to the magnetic field sensor element 140.

[0021] The first light-emitting unit 110 has a first light-emitting element 111, a first isolator 112, and a polarizer 113, and emits first linearly polarized light. The first light-emitting element 111 is, for example, a semiconductor laser or a light-emitting diode. Specifically, the first light-emitting element 111 may be a Fabry-Perot laser, a superluminescent diode (SLD), or the like. The first light-emitting element 111 emits light with a wavelength of, for example, 1550 nm.

[0022] The first isolator 112 transmits light incident from the first light-emitting element 111 to the optical unit 1 side, and does not transmit light incident from the optical unit 1 to the first light-emitting element 111 side, thereby protecting the first light-emitting element 111. The first isolator 112 is, for example, a polarization-dependent optical isolator, but may also be a polarization-independent optical isolator.

[0023] The polarizer 113 is an optical element for converting the light emitted by the first light emitting element 111 into linearly polarized light B1, and the type of the polarizer 113 is not particularly limited. The first linearly polarized light B1 obtained by the polarizer 113 is incident on the optical unit 1.

[0024] The second light-emitting unit 110a includes a second light-emitting element 111a, a second isolator 112a, and a depolarizer 113a, and emits unpolarized light. The second light-emitting element 111a is, for example, a semiconductor laser or a light-emitting diode. Specifically, the second light-emitting element 111a may be, for example, a Fabry-Perot laser or a superluminescent diode (SLD). The second light-emitting element 111a emits light with a wavelength of, for example, 1310 nm.

[0025] If the wavelength of the first linearly polarized light emitted by the first light-emitting element 111 is light in a first wavelength band, it is preferable that the wavelength of the unpolarized light emitted by the second light-emitting element 111a is light in a second wavelength band different from the first wavelength band. Furthermore, it is preferable that the first wavelength band is included in the C-band wavelength band (1530 to 1565 nm), and the second wavelength band is included in the O-band wavelength band (1260 to 1360 nm). Because the C-band wavelength band and the O-band wavelength band are close to each other, selecting such wavelength bands allows the optical system for the light emitted by the first light-emitting element 111 and the optical system for the light emitted by the second light-emitting element 111a to be the same.

[0026] The second isolator 112a protects the second light-emitting element 111a by transmitting the light incident from the second light-emitting element 111a to the optical unit 1 side and not transmitting the light incident from the optical unit 1 to the second light-emitting element 111a side. The second isolator 112a is, for example, a polarization-dependent optical isolator, but may also be a polarization-independent optical isolator.

[0027] The depolarizer 113a is an optical element for converting the light emitted by the second light emitting element 111a into unpolarized light, and the type of the depolarizer 113a is not particularly limited. The unpolarized light obtained by the depolarizer 113a is incident on the optical unit 1.

[0028] The optical unit 1 has a housing 10, a first port 11, a second port 12, a third port 13, a fourth port 14, a fifth port 15, and a sixth port 16, and adjusts the phase of incident light so that the phase difference between the outgoing first linearly polarized light B2P3 and the second linearly polarized light B2P4 is 90 degrees, and also emits returning light when unpolarized light is incident. The housing 10 is a storage section made of a material with high thermal conductivity such as aluminum, and arranges the various optical elements of the optical unit 1 in predetermined positions.

[0029] The first port 11 is an input port for inputting the first linearly polarized light B1 and unpolarized light, and is located at the center of one end face in the longitudinal direction of the housing 10, and receives the first linearly polarized light B1. The second port 12 is an input / output port for outputting incident light BI that is incident on the magnetic field sensor element 140, and for receiving return light BR from the magnetic field sensor element 140, and is located at the center of the other end face in the longitudinal direction of the housing 10.

[0030] The third port 13 is an output port that outputs the first linearly polarized light B2P3, and is located at one end of one of the longitudinal end faces of the housing 10. The fourth port 14 is an output port that outputs the second linearly polarized light B2P4, and is located at the other end of the longitudinal end face of the housing 10. That is, the third port and the fourth port respectively output a first linearly polarized light obtained by splitting the first linearly polarized light from the returning light, and a second linearly polarized light that is orthogonal to the first linearly polarized light.

[0031] Fifth port 15 is an output port that outputs return light P', which is a P-polarized component when unpolarized light is incident, and is located at one end of one end face perpendicular to the longitudinal direction of housing 10. Sixth port 16 is an output port that outputs return light S', which is an S-polarized component when unpolarized light is incident, and is located at the other end face perpendicular to the longitudinal direction of housing 10. That is, the fifth port and sixth port respectively output the P-polarized component and the S-polarized component obtained by splitting unpolarized return light from the return light.

[0032] The quarter-wave plate 120 is made of a birefringent material such as quartz, and is disposed with its optical axis tilted 45 degrees with respect to the direction of the polarization plane of the first linearly polarized light B1. The quarter-wave plate 120 converts the first incident polarized light BIP1 and the second incident polarized light BIP2, which are linearly polarized components of the incident light BI output from the second port 12, into circularly polarized light that is incident on the magnetic field sensor element 140, and outputs the circularly polarized light to the plano-convex lens 130. The quarter-wave plate 120 also converts the return light BR, which is incident as circularly polarized light from the magnetic field sensor element 140, into return light BRP1 and return light BRP2, which are linearly polarized components.

[0033] The plano-convex lens 130 focuses the incident light BI emitted from the quarter-wave plate 120 onto the magnetic field sensor element 140, and also focuses the returning light BR emitted from the magnetic field sensor element 140 onto the magnetic field sensor element 140.

[0034] The magnetic field sensor element 140 has a Faraday rotator 141 and a mirror element 142, and is an element at least a part of which can be placed in a predetermined magnetic field. The magnetic field sensor element 140 receives incident light BI from the plano-convex lens 130 and emits return light BR corresponding to the incident incident light BI to the plano-convex lens 130.

[0035] The Faraday rotator 141 is a granular film having a dielectric and nano-sized magnetic particles dispersed in the dielectric in a state where they are stably phase-separated from the dielectric, and is disposed at a distance from the plano-convex lens 130 by the focal length of the plano-convex lens 130. The magnetic particles may form oxides in a small portion, such as the outermost layer, but throughout the Faraday rotator 141, the magnetic particles are dispersed independently in the thin film without forming compounds with the dielectric, which serves as a binder. The distribution of the magnetic particles in the Faraday rotator 141 does not need to be completely uniform and may be slightly biased. If a highly transparent dielectric is used, the magnetic particles will be present in the dielectric at a size smaller than the wavelength of light, making the Faraday rotator 141 optically transparent.

[0036] The Faraday rotator 141 is not limited to a single layer, but may be a multilayer film in which granular films and dielectric films are alternately stacked. By forming the Faraday rotator 141 using a multilayer granular film, a larger Faraday rotation angle can be obtained due to multiple reflections within the granular film.

[0037] The dielectric is preferably a fluoride (metal fluoride) such as magnesium fluoride (MgF), aluminum fluoride (AlF), or yttrium fluoride (YF). Alternatively, the dielectric may be an oxide such as tantalum oxide (TaO), silicon dioxide (SiO), titanium dioxide (TiO), niobium pentoxide (NbO), zirconium dioxide (ZrO), hafnium dioxide (HfO), or aluminum trioxide (AlO). To achieve good phase separation between the dielectric and the magnetic particles, fluorides are preferred over oxides, and magnesium fluoride, which has high transmittance, is particularly preferred.

[0038] The material of the magnetic particles is not particularly limited as long as it produces the Faraday effect, but examples of the material for the magnetic particles include ferromagnetic metals such as iron (Fe), cobalt (Co), and nickel (Ni), as well as alloys thereof. Examples of alloys of Fe, Co, and Ni include FeNi alloys, FeCo alloys, FeNiCo alloys, and NiCo alloys. The Faraday rotation angle per unit length of Fe, Co, and Ni is two to three orders of magnitude larger than that of magnetic garnets used in conventional Faraday rotators.

[0039] The mirror element 142 is formed on the Faraday rotator 141 and reflects light transmitted through the Faraday rotator 141 back toward the Faraday rotator 141. The mirror element 142 may be made of, for example, a silver (Ag) film, a gold (Au) film, an aluminum (Al) film, or a dielectric multilayer mirror. Ag films with high reflectivity and Au films with high corrosion resistance are particularly preferred for their ease of film formation. The thickness of the mirror element 142 may be any thickness that ensures sufficient reflectivity of 98% or more. For example, in the case of an Ag film, the thickness is preferably 50 nm or more and 200 nm or less. By using the mirror element 142 to cause light to travel back and forth within the Faraday rotator 141, the Faraday rotation angle can be increased.

[0040] In the magnetic field sensor element 140, when the incident light BI propagates through the inside of the Faraday rotator 141 toward the mirror element 142, the phase is changed by θ in accordance with the magnetic field applied to the Faraday rotator 141.F On the other hand, no Faraday rotation occurs for the incident unpolarized light. When the return light BR reflected from the mirror element 142 propagates inside the Faraday rotator 141, the phase is changed by θ F The phase difference between the incident light BI and the return light BR is 2θ F is.

[0041] The detection signal generating unit 150 has a first light receiving element 151, a second light receiving element 152, and a first signal processing circuit 153, and receives the return light BR that has been split into a first linearly polarized light B2P3 and a second linearly polarized light B2P4 in the optical unit 1.

[0042] The first light receiving element 151 and the second light receiving element 152 are each, for example, a PIN photodiode. The first light receiving element 151 receives the first linearly polarized light B2P3, and the second light receiving element 152 receives the second linearly polarized light B2P4. The first light receiving element 151 and the second light receiving element 152 each photoelectrically convert the received light and output an electrical signal corresponding to the amount of light received. The first signal processing circuit 153 differentially amplifies the electrical signal representing the first linearly polarized light B2P3 and the electrical signal representing the second linearly polarized light B2P4, and outputs a detection signal Ed corresponding to the magnetic field applied to the magnetic field sensor element to a display device such as an oscilloscope.

[0043] 2 shows a circuit block diagram of the first signal processing circuit 153. The first signal processing circuit 153 has a first amplifier circuit 154, a second amplifier circuit 155, a first divider circuit 156, a second divider circuit 157, and a differential amplifier circuit 158. The first signal processing circuit 153 detects the difference in intensity between two polarized components from the electrical signals photoelectrically converted by the first light receiving element 151 and the second light receiving element 152, and converts the detected numerical value into a current value.

[0044] Each of the first amplifier circuit 154 and the second amplifier circuit 155 is an analog amplifier circuit formed by an operational amplifier, a resistor element, and the like.

[0045] The first amplifier circuit 154 receives a first electrical signal Ep1 corresponding to the light amount Lp of the P-polarized component B2P3 from the first light receiving element 151, amplifies the received first electrical signal Ep1, and outputs a first amplified electrical signal Ep2. The second amplifier circuit 155 receives a second electrical signal Es1 corresponding to the light amount Ls of the S-polarized component B2P4 from the second light receiving element 152, amplifies the received second electrical signal Es1, and outputs a second amplified electrical signal Es2.

[0046] Each of the first division circuit 156 and the second division circuit 157 is an analog division circuit formed by an operational amplifier, a resistance element, and the like.

[0047] The first division circuit 156 divides the first amplified electrical signal Ep2 by the second amplified electrical signal Es2 and outputs a first analog signal (Ep2 / Es2) indicating the divided output value to the negative input terminal of the differential amplifier circuit 158. The second division circuit 157 divides the second amplified electrical signal Es2 by the first amplified electrical signal Ep2 and outputs a second analog signal (Es2 / Ep2) indicating the divided output value to the positive input terminal of the differential amplifier circuit 158.

[0048] The differential amplifier circuit 158 ​​is, for example, an operational amplifier, and differentially amplifies the first analog signal (Ep2 / Es2) input from the first division circuit 156 and the second analog signal (Es2 / Ep2) input from the second division circuit 157, and outputs the detection signal Ed.

[0049] The crosstalk compensation circuit 160 has a third light receiving element 161, a fourth light receiving element 162, and a second signal processing circuit 163, and receives the return light P', which is a P-polarized component, and the return light S', which is an S-polarized component, separated in the optical unit 1, and converts them into electrical signals, thereby outputting a disturbance signal corresponding to the polarization crosstalk.

[0050] The third light receiving element 161 and the fourth light receiving element 162 are each, for example, a PIN photodiode. The third light receiving element 161 and the fourth light receiving element 162 receive the return light P' and S', respectively, when unpolarized light is incident thereon. The third light receiving element 161 and the fourth light receiving element 162 perform photoelectric conversion on the received light P' and S', and output an electrical signal corresponding to the amount of light received. The second signal processing circuit 163 differentially amplifies the electrical signals generated by the return light P' and S', and outputs a signal corresponding to crosstalk in the optical fiber.

[0051] 3 shows a circuit block diagram of the second signal processing circuit 163. The second signal processing circuit 163 has a third amplifier circuit 164, a fourth amplifier circuit 165, a third divider circuit 166, a fourth divider circuit 167, and a differential amplifier circuit 168. The second signal processing circuit 163 detects the difference in intensity between two polarized components from the electrical signals photoelectrically converted by the third light receiving element 161 and the fourth light receiving element 162, and converts the detected numerical value into a current value.

[0052] Each of the third amplifier circuit 164 and the fourth amplifier circuit 165 is an analog amplifier circuit formed by an operational amplifier, a resistor element, and the like.

[0053] The third amplifier circuit 164 receives a third electrical signal Ep1' corresponding to the light amount of the P-polarized component P' from the third light receiving element 161, amplifies the received third electrical signal Ep1', and outputs a third amplified electrical signal Ep2'. The fourth amplifier circuit 165 receives a fourth electrical signal Es1' corresponding to the light amount of the S-polarized component S' from the fourth light receiving element 162, amplifies the received fourth electrical signal Es1', and outputs a fourth amplified electrical signal Es2'.

[0054] Each of the third division circuit 166 and the fourth division circuit 167 is an analog division circuit formed by an operational amplifier, a resistance element, and the like.

[0055] The third division circuit 166 divides the third amplified electrical signal Ep2' by the fourth amplified electrical signal Es2' and outputs a third analog signal (Ep2' / Es2') indicating the divided output value to the positive input terminal of the differential amplifier circuit 168. The fourth division circuit 167 divides the fourth amplified electrical signal Es2' by the third amplified electrical signal Ep2' and outputs a fourth analog signal (Es2' / Ep2') indicating the divided output value to the negative input terminal of the differential amplifier circuit 168.

[0056] The differential amplifier circuit 168 is, for example, an operational amplifier, which differentially amplifies the third analog signal (Ep2' / Es2') input from the third division circuit 166 and the fourth analog signal (Es2' / Ep2') input from the fourth division circuit 167, and outputs a detection signal Ec. The detection signal Ec is a signal generated by crosstalk.

[0057] The signal processing circuit 170 receives the detection signal Ed from the detection signal generating unit 150 and the disturbance signal Ec output by the crosstalk compensation circuit 160, and outputs a differential signal between the detection signal Ed and the disturbance signal Ec. Specifically, the signal processing circuit 170 outputs a signal in which the influence of crosstalk has been reduced, based on the difference between the output signal Ed from the first signal processing circuit 153 of the detection signal generating unit 150 and the output signal Ec from the second signal processing circuit 163 of the crosstalk compensation circuit 160. That is, the output signal from the first signal processing circuit 153 contains the detection signal from the magnetic field sensor element 140 and crosstalk, while the output signal from the second signal processing circuit 163 contains only a signal corresponding to the crosstalk. Therefore, the signal processing circuit 170 can output only the detection signal from the magnetic field sensor element 140 in which the influence of crosstalk has been reduced by subtracting the output signal from the second signal processing circuit 163 from the output signal from the first signal processing circuit 153.

[0058] (Optical unit) FIG. 4 is a plan view of the optical unit 1. As shown in FIG.

[0059] The optical unit 1 further includes a first birefringent element 21, a second birefringent element 22, a third birefringent element 23, and a fourth birefringent element 24. The optical unit 1 further includes a first Faraday rotator 25, a second Faraday rotator 26, a first (½) wave plate 27, a second (½) wave plate 28, a first (¼) wave plate 29, and a second (¼) wave plate 30. The optical unit 1 further includes a first optical element 31, a second optical element 32, a first base 33, a second base 34, and a third base 35. The first birefringent element 21, the second birefringent element 22, the second Faraday rotator 26, the first (¼) wave plate 29, and the second (¼) wave plate 30 form an optical path section 20. The first birefringent element 21 to the second optical element 32, which are optical elements included in the optical unit 1, are spatially coupled without using optical fibers.

[0060] The first port 11 receives the first linearly polarized light B1 from the first light emitting unit 110 and outputs the received first linearly polarized light B1 to the first Faraday rotator 25.

[0061] The second port 12 receives incident light BI from the second birefringent element 22 onto the magnetic field sensor element 140 and outputs the incident light BI to the quarter-wave plate 120. The second port 12 also receives return light BR from the quarter-wave plate 120 and outputs the incident return light BR to the second birefringent element 22.

[0062] The third port 13 receives the first linearly polarized light B2P3 from the first optical element 31 and outputs the incident first linearly polarized light B2P3 to the first light receiving element 151. The fourth port 14 receives the second linearly polarized light B2P4 from the second optical element 32 and outputs the incident second linearly polarized light B2P4 to the second light receiving element 152.

[0063] The first birefringent element 21, the second birefringent element 22, the third birefringent element 23, and the fourth birefringent element 24 are birefringent elements made of, for example, calcite (CaCO3).

[0064] FIG. 5 is a diagram showing the optical characteristics of the first birefringent element 21. As shown in FIG.

[0065] The first birefringent element 21 has a first surface 21a, a second surface 21b, and an optical axis 21c, and inputs and outputs polarized light B propagating along a single optical path from the first surface 21a, while inputting and outputting first polarized light BP1 and second polarized light BP2 propagating along two optical paths from the second surface 21b. The first polarized light BP1 has a polarization plane in the horizontal direction in FIG. 5 and is also referred to as an ordinary ray. The second polarized light BP2 has a polarization plane in the vertical direction in FIG. 5 and is also referred to as an extraordinary ray. The first birefringent element 21 is positioned so that the optical axis 21c is oriented in a direction that allows the desired first polarized light BP1 and second polarized light BP2 to enter and exit.

[0066] When polarized light B is incident on the first surface 21a, the first birefringent element 21 separates the polarized light B into a first polarized light BP1 that propagates along the longitudinal direction of the first birefringent element 21 and a second polarized light BP2 that propagates at an angle oblique to the longitudinal direction of the first birefringent element 21. When polarized light B is incident on the first surface 21a, the first birefringent element 21 emits the first polarized light BP1 and the second polarized light BP2 from the second surface 21b. When the first polarized light BP1 and the second polarized light BP2 are incident on the second surface 21b, the first birefringent element 21 combines the first polarized light BP1 and the second polarized light BP2, and emits the polarized light B from the first surface 21a.

[0067] The second birefringent element 22, the third birefringent element 23 and the fourth birefringent element 24 have optical properties similar to those of the first birefringent element 21, and therefore detailed description thereof will be omitted.

[0068] The first birefringent element 21 is disposed so that its first surface 21a faces the second (½) wave plate 28 and its second surface 21b faces the first (¼) wave plate 29. The second birefringent element 22 is disposed so that its first surface 21a faces the second (¼) wave plate 30 and its second surface 21b faces the second port 12.

[0069] The third birefringent element 23 is disposed so that one surface faces the second (½) wave plate 28 and the other surface faces the first (½) wave plate 27. The fourth birefringent element 24 is disposed so that one surface faces the first Faraday rotator 25 and the other surface faces the first port 11, the first optical element 31, and the second optical element 32.

[0070] The first Faraday rotator 25 and the second Faraday rotator 26 are made of a ferromagnetic material such as bismuth iron garnet and shift the phase of the incident linearly polarized light and circularly polarized light by 45 degrees. The first Faraday rotator 25 is disposed between the fourth birefringent element 24 and the first (½) wave plate 27. The second Faraday rotator 26 is disposed between the first (¼) wave plate 29 and the second (¼) wave plate 30 and is also referred to as the second polarizing element.

[0071] The first (1 / 2) wave plate 27 and the second (1 / 2) wave plate 28 are formed of a birefringent material such as quartz, and are arranged with their optical axes tilted by 22.5 degrees with respect to the direction of the polarization plane of the first linearly polarized light B1 incident from the first light emitter 110, thereby shifting the phase of the incident linearly polarized light by 45 degrees. The first (1 / 2) wave plate 27 is arranged between the first Faraday rotator 25 and the third birefringent element 23. The second (1 / 2) wave plate 28 is arranged between the first birefringent element 21 and the third birefringent element 23, and is also referred to as the first polarizing element.

[0072] The first (1 / 4) wave plate 29 and the second (1 / 4) wave plate 30 are formed of a birefringent material such as quartz, and are arranged with their optical axes tilted 45 degrees with respect to the direction of the polarization plane of the first linearly polarized light B1 incident from the first light emitter 110, converting linearly polarized light into circularly polarized light and converting circularly polarized light into linearly polarized light. The first (1 / 4) wave plate 29 is arranged between the first birefringent element 21 and the second Faraday rotator 26. The second (1 / 4) wave plate 30 is arranged between the second birefringent element 22 and the second Faraday rotator 26.

[0073] The first optical element 31 and the second optical element 32 are rhomboid prisms. The first optical element 31 is disposed between the third port 13 and the fourth birefringent element 24 and includes a filter 310. The first linearly polarized light B2P3, which is light with a wavelength of 1550 nm and is output from the fourth birefringent element 24, is reflected by the filter 310 and output to the third port 13. On the other hand, the returning light with a wavelength of 1310 nm is transmitted through the filter 310 and output to the fifth port 15. In this way, the filter 310 separates the light with a wavelength of 1550 nm from the light with a wavelength of 1310 nm. The second optical element 32 is disposed between the fourth port 14 and the fourth birefringent element 24 and includes a filter 320. The second linearly polarized light B2P4, which is light with a wavelength of 1550 nm and is output from the fourth birefringent element 24, is reflected by the filter 320 and output to the fourth port 14. On the other hand, the returning light with a wavelength of 1310 nm passes through the filter 320 and is output to the sixth port 16. In this way, the filter 320 separates the light with a wavelength of 1550 nm from the light with a wavelength of 1310 nm.

[0074] The first base 33, the second base 34, and the third base 35 are each fixed to the housing 10. The first base 33 holds the first Faraday rotator 25 and the first (½) wave plate 27 between the third birefringent element 23 and the fourth birefringent element 24. The second base 34 holds the second (½) wave plate 28 between the third birefringent element 23 and the first birefringent element 21. The third base 35 holds the second Faraday rotator 26, the first (¼) wave plate 29, and the second (¼) wave plate 30 between the first birefringent element 21 and the second birefringent element 22.

[0075] FIG. 6(a) is a diagram showing the optical path of the first linearly polarized light B1 in the optical unit 1, and FIG. 6(b) is a diagram showing the transition of the polarization plane of the first linearly polarized light B1 shown in FIG. 6(a).

[0076] First, as indicated by arrow A, first linearly polarized light B1 having a wavelength of 1550 nm is incident from the first light-emitting unit 110 via the first port 11, and unpolarized light having a wavelength of 1310 nm is incident from the second light-emitting unit 110a via the first port 11. The first linearly polarized light B1 will be described below. The unpolarized light B1 travels through a similar optical path to become returned light, except that its wavelength is different from that of the first linearly polarized light B1 and that no Faraday rotation occurs in the magnetic field sensor element 140. Since the first linearly polarized light B1 is an ordinary ray, it propagates inside the fourth birefringent element 24 along the longitudinal direction of the fourth birefringent element 24.

[0077] Next, as shown by arrow B, the first linearly polarized light B1 is emitted from the fourth birefringent element 24 and enters the first Faraday rotator 25. The first linearly polarized light B1 undergoes a phase shift of 45 degrees while propagating inside the first Faraday rotator 25, and as shown by arrow C, is emitted from the first Faraday rotator 25 with a phase shift of 45 degrees and enters the first (½) wave plate 27.

[0078] The phase of the first linearly polarized light B1 is shifted by −45 degrees as it propagates inside the first (½) wave plate 27, and as shown by arrow D, its polarization plane returns before it enters the first Faraday rotator 25, and the first linearly polarized light B1 is emitted from the first (½) wave plate 27 and enters the third birefringent element 23. Since the first linearly polarized light B1 is an ordinary ray, it propagates inside the third birefringent element 23 along the longitudinal direction of the third birefringent element 23.

[0079] Next, as shown by arrow E, the first linearly polarized light B1 is emitted from the third birefringent element 23 and is incident on the second (½) wave plate 28. The first linearly polarized light B1 undergoes a phase shift of 45 degrees as it propagates through the second (½) wave plate 28, and as shown by arrow F, is emitted from the second (½) wave plate 28 with a phase shift of 45 degrees and is incident on the first birefringent element 21.

[0080] When the first linearly polarized light B1 enters the first birefringent element 21, it is split into a third linearly polarized light B1P1, which is an ordinary ray, and a fourth linearly polarized light B1P2, which is an extraordinary ray. Since the first linearly polarized light B1 is an ordinary ray, it propagates inside the first birefringent element 21 along the longitudinal direction of the first birefringent element 21.

[0081] As indicated by arrow G, the third linearly polarized light B1P1 exits the first birefringent element 21 and enters the first (¼) wave plate 29. The third linearly polarized light B1P1 is converted into the first circularly polarized light B1C1 while propagating through the first (¼) wave plate 29. As indicated by arrow H, the first circularly polarized light B1C1 exits the first (¼) wave plate 29 and enters the second Faraday rotator 26.

[0082] The first circularly polarized light B1C1 has its phase shifted by 45 degrees as it propagates through the second Faraday rotator 26, and is then output from the second Faraday rotator 26 and incident on the second (¼) wave plate 30, as indicated by arrow I. The first circularly polarized light B1C1 is converted into third linearly polarized light B1P1 as it propagates through the second (¼) wave plate 30. As indicated by arrow J, the third linearly polarized light B1P1 is output from the second (¼) wave plate 30 and incident on the second birefringent element 22.

[0083] On the other hand, the fourth linearly polarized light B1P2, which is an extraordinary ray, propagates inside the first birefringent element 21 at an angle inclined from the longitudinal direction of the first birefringent element 21. As indicated by arrow K, the fourth linearly polarized light B1P2 is emitted from the first birefringent element 21 and enters the second birefringent element 22.

[0084] In the second birefringent element 22, the third linearly polarized light B1P1 propagates through the second birefringent element 22 along the longitudinal direction of the second birefringent element 22. On the other hand, the fourth linearly polarized light B1P2 propagates through the second birefringent element 22 at an angle inclined from the longitudinal direction of the second birefringent element 22. As indicated by arrow L, the third linearly polarized light B1P1 and the fourth linearly polarized light B1P2 are combined and emitted from the second birefringent element 22 as incident light BI. Light BI' produced when unpolarized light is incident also exits from the second birefringent element 22.

[0085] FIG. 7(a) is a diagram showing the optical path of the second linearly polarized light B2 in the optical unit 1, and FIG. 7(b) is a diagram showing the transition of the polarization plane of the second linearly polarized light B2 shown in FIG. 7(a).

[0086] First, as indicated by arrow A, the return light BR and BR' enter through the second port 12 from the quarter-wave plate 120. The return light BR will be described below. The return light BR' follows the same optical path as the return light BR, except that its wavelength is different from that of the return light BR and that it does not undergo Faraday rotation. The return light BR has a fifth linearly polarized light B2P1 and a sixth linearly polarized light B2P2, which is a polarization component orthogonal to the fifth linearly polarized light B2P1.

[0087] When the return light BR enters the second birefringent element 22, it is split into a fifth linearly polarized light B2P1 and a sixth linearly polarized light B2P2. The fifth linearly polarized light B2P1 is an ordinary ray and therefore propagates through the second birefringent element 22 along the longitudinal direction of the second birefringent element 22. On the other hand, the sixth linearly polarized light B2P2 is an extraordinary ray and therefore propagates through the second birefringent element 22 at an angle oblique to the longitudinal direction of the second birefringent element 22.

[0088] As indicated by arrow B, the fifth linearly polarized light B2P1 is emitted from the second birefringent element 22 and enters the second (¼) wave plate 30. The fifth linearly polarized light B2P1 is converted into the third circularly polarized light B2C1 while propagating through the second (¼) wave plate 30. As indicated by arrow C, the third circularly polarized light B2C1 is emitted from the second (¼) wave plate 30 and enters the second Faraday rotator 26.

[0089] The third circularly polarized light B2C1 has its circularly polarized phase shifted by -45 degrees while propagating through the second Faraday rotator 26, and is then output from the second Faraday rotator 26 and incident on the first (¼) wave plate 29, as indicated by arrow D. The third circularly polarized light B2C1 is converted into fifth linearly polarized light B2P1 while propagating through the first (¼) wave plate 29. As indicated by arrow E, the fifth linearly polarized light B2P1 is output from the first (¼) wave plate 29 and incident on the first birefringent element 21.

[0090] On the other hand, the sixth linearly polarized light B2P2, which is an extraordinary ray, propagates inside the second birefringent element 22 at an angle inclined from the longitudinal direction of the second birefringent element 22. As indicated by arrow F, the sixth linearly polarized light B2P2 is emitted from the second birefringent element 22 and enters the first birefringent element 21.

[0091] In the first birefringent element 21, the fifth linearly polarized light B2P1 propagates inside the first birefringent element 21 along the longitudinal direction of the first birefringent element 21. On the other hand, the sixth linearly polarized light B2P2 propagates inside the first birefringent element 21 at an angle inclined from the longitudinal direction of the first birefringent element 21. As indicated by arrow G, the fifth linearly polarized light B2P1 and the sixth linearly polarized light B2P2 are combined and output from the first birefringent element 21 to the second (½) wave plate 28 as the fourth linearly polarized light B2.

[0092] The fourth linearly polarized light B2 is output from the second (½) wave plate 28 with its phase shifted by −45 degrees while propagating through the second (½) wave plate 28. As indicated by arrow H, the fifth linearly polarized light B2P1 and the sixth linearly polarized light B2P2 are each input to the third birefringent element 23 with their phases shifted by −45 degrees.

[0093] The fifth linearly polarized light B2P1 and the sixth linearly polarized light B2P2 are separated into a first linearly polarized light B2P3, which is an extraordinary ray, and a second linearly polarized light B2P4, which is an ordinary ray, when propagating inside the third birefringent element 23. Since the first linearly polarized light B2P3 is an extraordinary ray, it propagates inside the third birefringent element 23 at an angle oblique to the longitudinal direction of the third birefringent element 23, as shown by arrow I, exits the third birefringent element 23, and enters the first (½) wave plate 27.

[0094] The first linearly polarized light B2P3 undergoes a phase shift of -45 degrees as it propagates inside the first (1 / 2) wave plate 27, and as shown by arrow J, it exits the first (1 / 2) wave plate 27 with a phase shift of -45 degrees and enters the first Faraday rotator 25.

[0095] The first linearly polarized light B2P3 undergoes a further phase shift of -45 degrees as it propagates inside the first Faraday rotator 25, and as shown by arrow K, it is emitted from the first Faraday rotator 25 with a further phase shift of -45 degrees and enters the fourth birefringent element 24.

[0096] Since the first linearly polarized light B2P3 is an ordinary ray, it propagates inside the fourth birefringent element 24 along the longitudinal direction of the third birefringent element 23, as shown by arrow L, exits the fourth birefringent element 24, and enters the first optical element 31. Since the first linearly polarized light B2P3 has a wavelength of 1550 nm, it passes through the first optical element 31, is reflected by the filter 310, and exits from the third port 13. On the other hand, the returning light when unpolarized light is incident has a wavelength of 1310 nm, so it passes through the filter 310 and exits from the fifth port 15.

[0097] Since the second linearly polarized light B2P4 is an ordinary ray, it propagates inside the third birefringent element 23 along the longitudinal direction of the third birefringent element 23, as shown by arrow M, exits the third birefringent element 23, and enters the first (1 / 2) wavelength plate 27.

[0098] The second linearly polarized light B2P4 undergoes a phase shift of -45 degrees as it propagates inside the first (1 / 2) wave plate 27, and as shown by arrow N, it exits the first (1 / 2) wave plate 27 with a phase shift of -45 degrees and enters the first Faraday rotator 25.

[0099] The second linearly polarized light B2P4 undergoes a further phase shift of -45 degrees as it propagates inside the first Faraday rotator 25, and as shown by arrow O, it is emitted from the first Faraday rotator 25 with a further phase shift of -45 degrees and enters the fourth birefringent element 24.

[0100] Since the second linearly polarized light B2P4 is an extraordinary ray, it propagates through the fourth birefringent element 24 at an angle relative to the longitudinal direction of the third birefringent element 23, as indicated by arrow P, exits the fourth birefringent element 24, and enters the second optical element 32. Since the second linearly polarized light B2P4 has a wavelength of 1550 nm, it is reflected by the filter 320 after passing through the second optical element 32, and exits from the fourth port 14. On the other hand, the returning light when unpolarized light is incident has a wavelength of 1310 nm, and therefore passes through the filter 320 and exits from the sixth port 16.

[0101] (Actions and Effects of the Optical Unit According to the Embodiment) The optical unit 1 employs a birefringent element that can be made smaller than a beam splitter as an element that performs splitting and multiplexing processing, and therefore the interferometric optical magnetic field sensor device 100 can be made smaller than an interferometric optical magnetic field sensor device that uses a beam splitter. For example, the length of one side of a beam splitter is about 300 mm to 600 mm, whereas calcite, which is one of the birefringent elements, has a width and height of 30 mm and a length of 100 mm.

[0102] Furthermore, the optical unit 1 and the interferometric optical magnetic field sensor device 100 spatially couple the optical elements without placing an optical fiber in the optical path between the optical elements. By spatially coupling the optical elements, the optical unit 1 and the interferometric optical magnetic field sensor device 100 can be made smaller than an interferometric optical magnetic field sensor device in which an optical fiber is placed in the optical path between the optical elements.

[0103] Furthermore, calcite, which is one of the birefringent elements used in the optical unit 1, has a higher extinction ratio than a beam splitter. The optical unit 1 and the interferometric optical magnetic field sensor device 100 use a birefringent element with a higher extinction ratio than a beam splitter, and therefore have a higher S / N ratio than an interferometric optical magnetic field sensor device that uses a beam splitter.

[0104] (Modification of the optical unit according to the embodiment) In the optical unit 1, a first port 11, a third port 13, and a fourth port 14 are arranged on one surface in the longitudinal direction of the housing 10, a fifth port 15 is arranged on one surface perpendicular to the longitudinal direction of the housing 10, a sixth port 16 is arranged on the other surface perpendicular to the longitudinal direction of the housing 10, and a second port 12 is arranged on the other surface in the longitudinal direction of the housing 10. However, in the optical unit according to the embodiment, the first port 11 to the sixth port 16 may be arranged on one surface.

[0105] Figure 8 is a plan view of an optical unit 2 relating to a modified example, Figure 9 is an optical path diagram of the first linearly polarized light B1 in the optical unit 2 shown in Figure 8, and Figure 10 is an optical path diagram of the second linearly polarized light B2 in the optical unit 2 shown in Figure 8.

[0106] The optical unit 2 differs from the optical unit 1 in that it has a housing 40 instead of the housing 10. The optical unit 2 also differs from the optical unit 1 in that it has an optical element 41 instead of the second Faraday rotator 26 and the first (½) wave plate 27. The optical unit 2 also differs from the optical unit 1 in that it has a first optical path prism mirror 51 to a sixth optical path prism mirror 56. The optical unit 2 also differs from the optical unit 1 in that it has a first exit prism mirror 61 to a sixth exit prism mirror 66 instead of the first optical element 31 and the second optical element 32.

[0107] The configurations and functions of the components of the optical unit 2 other than the housing 40, the optical element 41, the first optical path prism mirror 51 to the sixth optical path prism mirror 56, and the first exit prism mirror 61 to the sixth exit prism mirror 66 are the same as the configurations and functions of the components of the optical unit 1 that are given the same reference numerals. Therefore, detailed description of the configurations and functions of the components of the optical unit 2 other than the housing 40, the optical element 41, the first optical path prism mirror 51 to the sixth optical path prism mirror 56, and the first exit prism mirror 61 to the sixth exit prism mirror 66 will be omitted.

[0108] In the housing 40, the second port 12, the fifth port 15, and the sixth port 16 are arranged on the same plane as the first port 11, the third port 13, and the fourth port 14. The optical element 41 is an element in which the second Faraday rotator 26 and the first (½) wave plate 27 are integrated.

[0109] The first optical path prism mirror 51 to the sixth optical path prism mirror 56 and the first exit prism mirror 61 to the sixth exit prism mirror 66 are all rectangular prism mirrors. The first optical path prism mirror 51 and the second optical path prism mirror 52 are disposed on an optical path that optically connects the first birefringent element 21 and the first (¼) wave plate 29, and reverse the optical path.

[0110] The third optical path prism mirror 53 to the sixth optical path prism mirror 56 are disposed on an optical path that optically connects the first birefringent element 21 and the second birefringent element 22. The third optical path prism mirror 53 and the fourth optical path prism mirror 54 invert the optical path between the first birefringent element 21 and the second birefringent element 22. The fifth optical path prism mirror 55 and the sixth optical path prism mirror 56 shift the optical path between the first birefringent element 21 and the second birefringent element 22 toward the inside in the short side direction of the housing 40.

[0111] The first exit prism mirror 61 and the second exit prism mirror 62 optically connect the fourth birefringent element 24 and the third port 13, similar to the first optical element 31. The first exit prism mirror 61 and the fifth exit prism mirror 65 optically connect the fourth birefringent element 24 and the fifth port 15, similar to the first optical element 31. Furthermore, the third exit prism mirror 63 and the fourth exit prism mirror 64 optically connect the fourth birefringent element 24 and the fourth port 14, similar to the second optical element 32. The third exit prism mirror 63 and the sixth exit prism mirror 66 optically connect the fourth birefringent element 24 and the sixth port 16, similar to the second optical element 32.

[0112] The optical unit 1 also includes optical elements that split the second linearly polarized light B2 into the first linearly polarized light B2P3 and the second linearly polarized light B2P4, such as the third birefringent element 23 and the fourth birefringent element 24. However, the optical unit according to the embodiment does not necessarily have to include optical elements that split the second linearly polarized light B2.

[0113] Furthermore, the optical unit 1 splits the second linearly polarized light B2 using two birefringent elements, the third birefringent element 23 and the fourth birefringent element 24, but the optical unit according to the embodiment may split the second linearly polarized light B2 using a single birefringent element or three or more birefringent elements.

[0114] Furthermore, in the optical unit 1, the first birefringent element 21 to the second birefringent element 22 are made of calcite, but in the optical unit according to the embodiment, the birefringent elements may be made of a birefringent material other than calcite.

[0115] For example, in the optical unit according to the embodiment, the birefringent element may be formed of quartz (SiO), rutile (TiO), and corundum (sapphire, AlO). When light having a wavelength of 589.3 nm is incident, the refractive index of calcite for the ordinary ray is 1.6584 and the refractive index of the extraordinary ray is 1.4864. When light having a wavelength of 589.3 nm is incident, the refractive index of quartz for the ordinary ray is 1.5443 and the refractive index of the extraordinary ray is 1.5534. When light having a wavelength of 589.3 nm is incident, the refractive index of rutile for the ordinary ray is 2.6160 and the refractive index of the extraordinary ray is 2.903. When light having a wavelength of 589.3 nm is incident, the refractive index of corundum for the ordinary ray is 1.768 and the refractive index of the extraordinary ray is 1.7600. [Explanation of symbols]

[0116] 1, 2 Optical unit 10. Cabinet 11 Port 1 12 Second port 13 Third Port 14 4th Port 15 5th Port 16 6th Port 21 first birefringent element 22 Second birefringent element 23 Third birefringent element 24 Fourth birefringent element 25 First Faraday rotator 26 Second Faraday rotator (second polarizing element) 27 1st (1 / 2) wave plate 28 Second (1 / 2) wave plate (first polarizing element) 100 Interference type optical magnetic field sensor device 110 First light-emitting part 110a second light-emitting unit 120 1 / 4 wave plate 130 Plano-convex lens 140 Magnetic field sensor element 150 detection signal generator 160 Crosstalk compensation circuit 170 Signal Processing Circuit

Claims

1. a first light emitting unit that emits first linearly polarized light; a second light emitting unit that emits unpolarized light; a magnetic field sensor element, at least a portion of which can be placed within a predetermined magnetic field, which emits return light in response to incident light; an optical unit having a first port into which the first linearly polarized light and the unpolarized light are incident, a second port that emits the incident light to the magnetic field sensor element and into which the returned light is incident, a third port and a fourth port that respectively emit first linearly polarized light and second linearly polarized light orthogonal to the first linearly polarized light obtained by splitting the first linearly polarized light from the returned light, and a fifth port and a sixth port that respectively emit P-polarized component and S-polarized component obtained by splitting the unpolarized returned light from the returned light; a detection signal generating unit that receives the first linearly polarized light and the second linearly polarized light and converts them into electrical signals, thereby outputting a detection signal corresponding to a magnetic field applied to the magnetic field sensor element; a crosstalk compensation circuit that receives the P-polarized component and the S-polarized component and converts them into electrical signals to output a disturbance signal corresponding to the polarization crosstalk; a signal processing circuit that receives the detection signal and the disturbance signal and outputs a difference signal between the detection signal and the disturbance signal; An interference type optical magnetic field sensor device comprising:

2. the wavelength of the first linearly polarized light is light in a first waveband, the wavelength of the unpolarized light is light in a second wavelength band different from the first wavelength band; 2. The interference type optical magnetic field sensor device according to claim 1.

3. the first wavelength band is included in the C-band wavelength band, The second wavelength band is included in the O-band wavelength band.

3. The interference type optical magnetic field sensor device according to claim 2.

4. The optical unit comprises: a first polarizing element that, in response to the first linearly polarized light being incident thereon, emits third linearly polarized light and fourth linearly polarized light orthogonal to the third linearly polarized light, and that, in response to the fifth linearly polarized light and sixth linearly polarized light orthogonal to the fifth linearly polarized light being incident thereon, emits second linearly polarized light; an optical path unit optically connected to the first polarizing element, the optical path unit having a first optical path that propagates the third linearly polarized light and the sixth linearly polarized light, and a second optical path that propagates the fourth linearly polarized light and the fifth linearly polarized light; a third birefringence element that, in response to the second linearly polarized light being incident from the first polarizing element, demultiplexes the second linearly polarized light into a first linearly polarized light and a second linearly polarized light orthogonal to the first linearly polarized light, The optical path section includes: a first birefringence element that separates the third linearly polarized light and the fourth linearly polarized light incident from the first polarization element into the first optical path and the second optical path, respectively, and combines the fifth linearly polarized light that has propagated through the second optical path and the sixth linearly polarized light that has propagated through the first optical path, and outputs the combined light to the first polarization element; a second birefringence element that combines the third linearly polarized light that has propagated through the first optical path and the fourth linearly polarized light that has propagated through the second optical path and outputs the combined light to the second port, and that separates the fifth linearly polarized light and the sixth linearly polarized light that have entered from the second port into the first optical path and the second optical path, respectively.

4. The interference type optical magnetic field sensor device according to claim 1.

5. 5. The optical path section further includes a second optical element disposed in the first optical path, which adjusts the phase of the third linearly polarized light and the sixth linearly polarized light so that the phase difference between the fifth linearly polarized light and the sixth linearly polarized light is 90 degrees. The interference type optical magnetic field sensor device according to claim 4.

6. The interference type optical magnetic field sensor device according to claim 4 or 5, further comprising a third birefringence element that, in response to the second linearly polarized light being incident from the first polarizing element, splits the second linearly polarized light into a first linearly polarized light and a second linearly polarized light that is orthogonal to the first linearly polarized light.

7. a fourth birefringent element onto which the first linearly polarized light and the second linearly polarized light are incident from the third birefringent element, the first linearly polarized light is incident on the third port from the fourth birefringent element, the second linearly polarized light is incident on the fourth port from the fourth birefringent element; 7. An interference type optical magnetic field sensor device according to claim 6.

8. 8. The interference type optical magnetic field sensor device according to claim 7, wherein the first birefringent element, the second birefringent element, the third birefringent element, and the fourth birefringent element are made of calcite.

9. 9. The interferometric optical magnetic field sensor device according to claim 4, wherein the first birefringent element and the second birefringent element are spatially coupled.

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